1. Field of the Invention
The present invention relates to a magnetic tape recording/reproducing apparatus for recording and reproducing digital data supplied from for example an external computer.
2. Description of the Related Art
A magnetic tape recording/reproducing apparatus that is used as an external storage unit for a computer is known. In this case, a drive unit that loads a digital cassette tape is connected to a host computer through an interface. As an example of the data recorder, a helical scan type recorder that records digital data on a cassette tape with a rotating head is known.
Such a data recorder is connected to for example a SCSI (Small Computer Interface System) standard interface. Since the host computer recognizes the interface unit as a data recorder, it has a function for generating a file format on a tape and sending/receiving data to/from the tape (this function is referred to as formatter). The interface unit has a buffer memory that temporarily stores data transmitted between the host computer and the data recorder.
When an uncorrected error that cannot be corrected by signal processes such as a data recording process and a signal reproducing process takes place, with data temporarily stored in a buffer memory, write retry/read retry operations can be performed for the magnetic tape. For example, when data is read from the buffer memory and recorded on the tape for every buffer unit, the write retry operation is performed at an area (including a non-record area) followed by an invalid area in which data has not been recorded. When data is reproduced, the read retry operation is performed from an area in which data has not been reproduced.
As described above, the write retry operation and the read retry operation for data are certainly effective if a magnetic tape is partially damaged. However, in the case that dregs adhere on the tape or that magnetic particles of the magnetic tape adhere on a recording head or a reproduction head (this situation is referred to as head clogging), even if the different heads are used, since the tape with dregs is used, the write retry operation and the read retry operation for data cannot be performed. Alternatively, even if the different tape is used or the record area on the tape is changed, since the heads with dregs are used, the write retry operation and the read retry operation for the data cannot be performed.